Method for the automatic calculation optimum routes

ABSTRACT

A method for automatically calculating optimum routes in a traffic-route network is provided, taking into consideration at least one set, fixed route section, where the traffic-route network is described by segments for traffic-route sections, weighted with a resistance, and nodes for the intersection points of traffic-route sections, and the route to be calculated runs from a starting segment to a destination segment, and where, for purposes of optimization, the segments from the destination segment to the starting segment are evaluated with respect to the best resistance. The route is optimized, in each instance, from a starting segment up to the fixed route sections, at the fixed route sections, and from the fixed route section up to a destination segment.

FIELD OF THE INVENTION

The present invention relates to a method for automatically calculatingoptimum routes in a traffic-route network, in view of at least one set,fixed route section, the traffic-route network being described byresistance-weighted segments for traffic-route sections and nodes forthe intersection points of traffic-route sections, and the route to becalculated running from a starting segment to a destination segment,where, for purposes of optimization, the segments from the destinationsegment to the starting segment are evaluated for the most favorableresistance.

BACKGROUND INFORMATION

In a conventional navigation system, routes in a traffic-route networkare determined between set starting and destination points usingoptimization.

For mathematical processing, a traffic-route network is represented as agraph having segments k for road sections and nodes p for trafficjunctions. The segments represent the roads, and the nodes represent theinterconnection points of the road network. Since the traffic flow isdirectional in the real road network, a segment is described as adirectional vector.

The segments are assigned section resistances. The section resistancerepresents a parameter for the effort in traveling from one node in thetraffic-route network to another node. In the simplest case, the segmentlength can be directly used as the section resistance. As analternative, the travel time on a segment can also be regarded as itssection resistance, assuming a particular traffic speed (slow, medium,fast). However, optimization methods are also known, in which traveltime, length, and other variables are linked each other, in order tocalculate the section resistance of a segment in a graph.

It is known in the art that the nodes can each be assigned a maneuveringresistance.

An optimum route from a starting point on a starting segment to adestination point on a destination segment is determined byconventional, best-way route calculation algorithms such a that the sumof all the section resistances assigned to the segments of the optimumroute is minimized.

A standard algorithm for route optimization is described in Ford, Mooreand explained in detail in the following.

The best-way route optimization algorithm is reverse iterating, with allof the segments in the graph of the traffic-route network between thestarting segment and the destination segment being visited and evaluatedfor the most favorable resistance to the destination segment. Startingout from a destination segment, the route most favorable in terms ofresistance to the segments, which are specified in a list and optimizedin the previous iteration step, is visited here in each iteration step.As a result, the method supplies the optimum route from each segment inthe graph to the destination segment. The calculation results are storedin a route table in which the resistance up to the destination segmentand the subsequent successor segment in the destination direction isspecified for each segment in the graph of the traffic-route network.The resistance of each segment is set to “infinite” and the successorsegment is set to “undefined” as initialization values. In eachinstance, a resistance and a successor segment in the direction of thecorresponding segment is stored for each segment, as well as aresistance and a successor segment in the direction opposite to theresistance.

Prior to the start of the iterative optimization, the destinationsegment is initialized to have a resistance of zero in the route table.In addition, the destination edge is entered into a final list forsegments that are already optimized. A further optimization list isneeded for storing the segments to be checked in the next optimizationsteps.

This optimization list is empty at the start of the method.

The optimization method is begun after the initialization, all of thesegments specified in the final list being considered imaginary, actualpositions of a vehicle. All of the incoming segments interconnected withthis actual segment are subjected to an optimization test. For theoptimization, it is assumed that the vehicle is situated on one of theincoming segments, with the direction of travel towards the actualsegment. As an optimization condition, it is then checked if theresistance of the old, available route of the incoming segment is worsethan the resistance for the new route of the incoming segment, using theactual segment. If the route through the actual segment turns out to bemore optimal, the optimization is accomplished by entering thecorresponding, optimum resistances and successor segments for therespective incoming segments.

The condition for optimizing the resistances may be mathematicallyrepresented as follows:R _(RT, actual segment) +R _(segment, incoming segment) <R_(RT-old, INCOMING segment),where R_(RT, actual segment) is the resistance from the route table, ofthe considered, actual segment to the destination;R_(segment, incoming segment) is the segment resistance of an incomingsegment interconnected with the actual segment, and

R_(RT-old, INCOMING segment) is the resistance from the route table, ofthe incoming segment interconnected with the actual segment, to thedestination.

Optimization takes place when the above-mentioned inequality conditionis satisfied, i.e., the new resistance of the incoming segment is lessthan the old resistance of the incoming segment. The resistance of theincoming segment is replaced in the route table with the new, lesservalue. The actual segment is entered in as the successor segment, andthe optimized, incoming segment is introduced into the final list.

If all of the segments from the optimization list have been processed,as described, then the optimization list and the final list areinterchanged. The basis for the next optimizations are the segmentsoptimized here in the last step. The method is terminated when the finallist is found to be empty, i.e., when there are no more segmentsoptimized in the previous run.

In conventional navigation systems, a route to be optimized may beinfluenced by the user, for example, by

-   -   choosing different optimization criteria, such as a short route,        fast route, or avoidance of expressways, etc.;    -   controlling road sections manually, or by way of traffic        telematics, the road sections then being able to be driven        around or favored during the calculation of the optimum route;        and    -   defining one or more intermediate destinations, which are then        approached in order, in order to finally lead to a destination.

Besides defining intermediate destinations, the user has, however, nopossibility of presetting a particular section of his route, whichnecessarily becomes a part of the route between the starting segment andthe destination segment. Thus, there is the need, for example, tostipulate a route along tourist streets as a fixed route section, for,in different regions, certain streets are identified as tourist streets,which run along predetermined objects or have other special features.Thus, a wine trail, china street, or avenue, as well as a romanticstreet, are known, for example, in Germany.

In addition, there is a need to establish external definitions ofroutes. This is useful, for example, when the user should use particularroads on his way to the destination.

However, the stipulation of a fixed route section to be used should notbe completely obligating. In the event of a deviation from the fixedroute section, the route calculation unit should lead the driver back tothe fixed route section, taking the local conditions into consideration,but it should not lead the driver back by compelling him to turn around(compulsory turning-around).

Conventional navigation systems do not allow route sections to be fixedin advance.

The “TravelPilot DX-N” navigation system allows a user to define a tour,in that the fixed route section is described by intermediatedestinations. However, the conventional route-optimization algorithms donot ensure that the fixed route section is universally used. Inaddition, the route from the current vehicle position to the destinationis not calculated in this navigation system.

Therefore, an object of the present invention is to provide an improvedmethod for automatically calculating optimum routes in a traffic-routenetwork, in view of at least one set, fixed route section, where thecalculated, optimized route leads through as large a part of the fixedroute section as possible and the individual route sections are optimal.

SUMMARY OF THE INVENTION

This object to the present invention is achieved by optimizing theroute, in each instance, from the starting segment to the fixed routesection, and from the fixed route section to the destination segment.

This may be accomplished by:

-   a) dividing up the route into two route segments, a first starting    route segment (or first route portion) running from the starting    segment to approximately the end of the fixed route section, and a    second destination route segment (or second route portion) running    from approximately the end of the fixed route section to the    destination segment;-   b) separately optimizing the routes for the starting route segment    and for the destination route segment, a route being established as    optimal for an incoming segment, which is interconnected, in each    instance, with the actual segment to be tested,    -   when either the resistance of the route in the specific route        segment recently stipulated as being optimal for the incoming        segment is less optimal than the resistance of the new route in        the specific route segment starting out from the incoming        segment, using the actual segment,    -   or the resistance of the route in the specific route segment        recently established as being optimal for the incoming segment        corresponds to the resistance of the new route in the specific        route segment starting out from the incoming segment, using the        actual segment, and when the total resistance of the route        established up to now as being optimal for the incoming segment        in relation to the entire route is less optimal than the total        resistance of the new overall route starting from the incoming        segment, using the actual segment; and-   c) determining the optimum segment from the results of the    optimization for the starting route segment and the destination    route segment.

The separation of the optimization in the starting route segment and inthe destination route segment ensures optimum route guidance to thefixed route section and on the fixed route section, and optimum routeguidance from the fixed route section to the destination segment.

In addition to the known optimization condition, which is applied,however, so as to be limited to the specific route segment and not tothe entire route, optimization also occurs when the new resistance ofthe incoming segment corresponds to the previous resistance of theincoming segment, based on the specific route segment, and the totalresistance of the incoming segment, based on the entire route, issimultaneously more optimal than the previous resistance of the incomingsegment for the entire route.

This additional condition results in route guidance through the fixedroute section, if possible.

In addition, the method of the present invention has the advantage, thatthe complete route is available at all times and optimum route guidanceis also ensured after a change in or manipulation of the traffic-routenetwork by means of, for example, telematic control or user-definedblocking, or after a deviation from the previous route.

After the starting and destination route segments are optimized, theresults of the starting and destination route segments are compiled inthe form of a route list for the optimum route.

According to one embodiment, the optimization method according to theinvention is executed in the following order:

-   a) optimizing the route in the destination route segment;-   b) optimizing the route in the starting route segment; and-   c) determining the optimum segment from the results of the    optimization for the starting route segment and the destination    route segment.

In this connection, it is taken into account that the optimizationmethod is executed in a reverse-iterating manner and starts out from thedestination segment.

For both the starting route segment and the destination route segment, aroute table having all possible segments of the traffic-route network isadvantageously initialized for the route in the specific route segment.According to the initialization, each segment may have, in eachinstance, one resistance per direction of a segment, and a subsequentsegment number. For the initialization, the resistances are set to anextreme value and the subsequent segments are stipulated as being“undefined”. The extremely high resistance (such as infinite) ensuresthat the above-described, optimization-condition inequality is initiallysatisfied and all segments are initially updated.

In order to optimize the route in the destination-route segment, theoriginal segments from which the optimization is started are alsoinitialized. To this end, the resistance of the original segments is setto zero in the route table, and the corresponding, successor segment isset to “not available” in the route table. For the destination routesegment, the original segments are all segments that belong to adestination.

To optimize the route in the starting route segment, the originalsegments are initialized in a different manner. The starting segments ofthe destination route segment having the lowest resistance up to thedestination segment are used as the original segment. In each instance,the total resistance of the original segments is set to the valuedetermined for the original segment during the optimization of thedestination route segment. The starting route segment-based resistancesof all segments of the fixed route section are set to zero. This allowsthe fixed route section to be considered during the route optimization.

In each instance, the initialization may be carried out at the start ofthe optimization of the starting route segment and the destination routesegment. The specific optimization method is subsequently carried out.

In order to detect the segments belonging to the fixed route section, astatus identifier may be provided in the route table for thecorresponding segments of the fixed route segment.

During the implementation of the method, it is advantageous to storepreviously optimized segments in a final list, and to access the finallist. A further optimization list may be provided for storing thesegments to be checked in the next optimization step which may be emptyat the start of the optimization method.

In this connection, the optimization method is iteratively executed forthe segments entered in the final list, these entered segments beingregarded as actual segments. The incoming segments corresponding to eachof these actual segments are optimized. The segments, which are to bechecked in the next optimization step and are entered into theoptimization list, result from the successor segments of the optimizedincoming segments. When the optimization is carried out for all actualsegments from the final list, the final list is interchanged with theoptimization list. The optimization is ended when the final list remainsempty after the exchange of the lists, i.e., when no more segments havebeen optimized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of a conventional navigation system forautomatically calculating optimum routes in a traffic-route network.

FIG. 2 shows a graphical diagram of a traffic-route network, having afixed route section.

FIG. 3 shows a graphical diagram of the traffic-route network from FIG.1, having route optimization according to a conventional optimizationmethod.

FIG. 4 shows a schematic representation of the division of a route intoa starting route segment and a destination route segment.

FIG. 5 shows an example flowchart of the method of the present inventionfor automatically calculating optimum routes.

FIG. 6 shows an example flowchart of the method for optimizing the routein the starting route segment.

FIG. 7 shows an example flowchart of the method for optimizing the routein the destination route segment.

FIG. 8 shows a graphical diagram for optimizing a considered, actualsegment having two incoming segments interconnected with it;

FIG. 9 shows an example flowchart of the checking of the optimizationconditions.

FIG. 10 shows an example flowchart of the method for optimizing theroute of a route segment.

FIG. 11 shows a graphical diagram of an example traffic-route network,having a vehicle on a starting segment, and having a destinationsegment.

FIG. 12 shows the graphical diagram from FIG. 11, having an optimizedroute after a first optimization step.

FIG. 13 shows the graphical diagram from FIG. 11, having an optimizedroute after a second optimization step.

FIG. 14 shows a sketch of the positioning of an example route outside ofa fixed route section.

FIG. 15 shows a sketch of an example route that uses an intermediatedestination in a fixed route section.

FIG. 16 shows a sketch of a route, using a route region.

FIG. 17 shows an example route which uses a fixed route section and isoptimized according to the method of the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a conventional navigation system 1 having a navigationcomputer 2 in the form of a block diagram. The position of a vehicle isdetermined with the aid of suitable sensors 3, such as a globalpositioning system (GPS) and/or wheel sensors, etc., and is transmittedto navigation computer 2 as a position signal. Navigation computer 2carries out position-finding 4. The position-finding signal is used fora route search 5. During route search 5, a digital map stored in a massmemory 6 may be accessed. The located position, the route, and, ifapplicable, further data are transmitted via an interface 7 to aloudspeaker 8, a display unit 9, and/or other output devices. An inputunit 10 is provided, in order to operate navigation system 1 and, inparticular, to define a starting position and a destination position.Input unit 10 is coupled to route search unit 5 by interface 7.

Specific route sections, which are to be considered in the optimizationof a route, may be input via input unit 10 and interface 7. Theseentries are stored in an index 11, which is coupled to route-search unit5.

Index 11 and interface 7 are adapted so that a fixed route section maybe set.

Using graphically supported, best-way route optimization algorithms, anoptimum route from the input destination point to a starting point iscalculated by navigation system 1.

FIG. 2 shows a traffic-route network 12 in the form of a graphicaldiagram. The exemplary traffic-route network is made up of segments k1,k2, k3, k4, k5, k6, k7, k8, k9, and k10. The interconnection orintersection points of segments are referred to as nodes p1, p2, p3, p4,p5, p6, p7, and p8. Defined starting point 13 is situated on segment k1and delineated as the vehicle position. Destination 14 designated by aflag is situated on segment k7. The segments themselves correspond totraffic-route sections or road sections.

A route through segments k8, k9, and k10 was defined by a user as apreferred route, which is subsequently designated as fixed route section15 and displayed with hatching. Such a fixed route section 15 may runalong tourist roads, for example, or may be another preferred route.

FIG. 3 shows the graphical diagram from FIG. 2, having an optimizedroute along segments k1, k2, k3 and k7 from starting point 13 todestination 14, the route having been optimized with the aid of aconventional, best-way route optimization algorithm. Since theconventional, best-way route optimization algorithms are not designed toconsider fixed route sections 15, the optimized route does not runthrough fixed route section 15.

As sketched in FIG. 4, the division of the routes into two routesegments 16 and 17 is provided for the method of the present inventionfor automatically calculating optimum routes, a first starting routesegment 16 running from starting point 13 to approximately the end offixed route section 15. Second destination route segment 17 runs fromthe end of starting route segment 16, i.e., from approximately the endof fixed route section 15, to destination 14.

In contrast to conventional, best-way route optimization algorithms, thepresent invention provides for the route optimization for starting routesegment 16 and destination route segment 17 to be accomplishedseparately.

FIG. 5 shows an example flowchart of the method of the present inventionfor automatically calculating optimum routes, the separate routecalculation for the two route segments 16 and 17 indicated in theflowchart.

After the start of an automatic calculation of an optimum route in atraffic-route network, the segments of the route section 15 to be fixedare initially determined, e.g., via index 11, and stored in a passinglist PassList in a first step a).

The optimization of the route in destination route segment 17 thenoccurs in a second step b). The optimization of the route in startingroute segment 16 in a third step c) only occurs after an optimum routehas been determined for destination route segment 17.

In a fourth step d), a final route list is compiled from the optimumroutes from the second and third steps of the method after completion ofthe route optimization in starting route segment 16, and the automaticcalculation method for an optimum route is ended.

FIG. 6 shows an example flowchart for optimizing the route indestination route segment 17. After the start of the procedure, a routetable is first initialized. In this connection, the resistances of thesegments are set to a value of “infinite”. The specific successors forthe resistances are set to “undefined” (−) (step D1).

The segments from a destination list (DestList) are initialized in asecond step D2. These are the segments belonging to destination 14. Theresistance of these segments is set to zero, while correspondingsuccessors are set to not available (NIL).

An optimization of the segments, which is expanded beyond the known,best-way route optimization algorithms and based on the graph theory, isperformed in step D3, the graph theory being subsequently explained indetail. The partial method is concluded after the segments for the routein starting route segment 16 are optimized.

FIG. 7 shows the corresponding method of third step c) for optimizingthe route in starting route segment 16.

In first step L1, the route table is initialized again, all of thesegments belonging to starting route segment 16 being input into theroute table, and the corresponding resistances are set to “infinite”.The specific successors of the resistances are set to “undefined” (−).The starting route segment is initialized in a second step L2, and thesegments from passing list (PassList) are designated as such in theroute table. Since the optimization method is carried out in a known,reverse-iterating manner, the segments from which the optimizationstarts are initialized. For starting route segment 16, these are thesegments of fixed route section 15 having the lowest resistance todestination 14 of destination route segment 17.

For these segments, the resistance previously determined during theoptimization of the route in destination route segment 17 is entered inthe route table, and the successor is appropriately designated. Inaddition, the resistance for all of the segments of fixed route section15 is set to zero.

An expanded optimization of the segments then occurs in third step L3.This method corresponds to step D3 during the optimization of the routein the destination route segment.

The expanded optimization method of the segments in the rearwardlydirected, iterative method is explained in detail in the following withreference to FIG. 8, which shows optimization relationships of segmentsk at node p. Starting out from an actual segment k1, which represents animaginary vehicle position, all of the so-called incoming segment(s)interconnected with actual segment k1 are checked. In the example shown,actual segment k1 is directed at destination 14. Incoming segments k2and k3 abut against actual segment k1 at a node p2.

Optimization relationships 01A, 01B und 01C are checked for theoptimization. Optimization relationship 01A represents turning around atnode p2 of actual segment k1 and takes the positive and negativeresistance of actual segment k1 into consideration.

Optimization condition 01B considers the resistances of incoming segmentk2 in the positive direction and the positive resistance of actualsegment k1 in the direction of destination 14.

Optimization relationship 01C considers the negative resistance ofincoming segment k3 (in the direction opposite to the arrow), as well asthe positive resistance of actual segment k1.

Starting out from the considered destination segments of specific routesegment 16 or 17, the starting segments of the course of the partialroute optimized in the previous optimization step are each used asactual segments in the rearwardly directed, iterating optimizationmethod.

FIG. 9 shows an example flowchart of the optimization rule of thepresent invention, according to which a segment within a route isestablished as being optimal. The optimization method is used in thesame way in steps D3 and L3 for optimizing the route in destinationroute segment 17 and starting route segment 16.

For each incoming segment, it is first checked if resistance R^(seg)_(RT, actual) of the actual segment, entered in the route table, basedon the corresponding route segment, plus resistanceR_(segment, incoming) of the incoming segment is less than oldresistance R_(RT-old, incoming) of the incoming segment to thedestination, entered in the route table, in specific route segment Seg,i.e., ifR ^(seg) _(RT, actual) +R _(segment, incoming) <R ^(seg)_(RT-old, incoming).

When this sufficient condition is satisfied, the entry for thecorresponding incoming segment is updated in the route table, in thatthe resistance values of the incoming segment are entered in the routetable and the actual segment is entered as a successor.

In the case in which the old, route-segment-based resistance of theincoming segment entered in the route table is greater than the sum ofthe resistance of the actual segment for the route segment, entered inthe route table, plus the resistance of the incoming segment, thesegment optimization for the is checked, and the incoming segment isended.

In the case of an equality, a further analysis of the total resistancesis conducted, which is based on the entire traffic-route network,regardless of the division into starting and destination route segments16, 17. In this connection, it is checked if the total resistance of theactual segment entered in the route table, plus the resistance of theincoming segment, is less than the total, incoming-segment resistance todestination 14 previously entered in the route table. If this conditionis satisfied, the entry in the route table is updated, as describedabove, in that the resistance values of the incoming segment, as well asthe actual segment, are entered in the route table as successors.

The condition for analyzing the total resistance may be mathematicallyrepresented as follows:(R ^(seg) _(RT, actual) +R _(segment, incoming) =R ^(Seg)_(RT-old, incoming))∩(R ^(total) _(RT, actual) +R _(segment, incoming)<R ^(total) _(RT-old, incoming))where

-   R^(seg) _(RT, actual): is the resistance of the actual segment to    the destination in specific route segment Seg, from the route table,-   R_(segment, incoming): is the segment resistance of the incoming    segment,-   R^(Seg) _(RT-old, incoming): is the resistance of the incoming    segment to the destination in specific route segment Seg, from the    route table,-   R^(total) _(RT, actual): is the resistance of the actual segment to    absolute destination 14 from the route table, and-   R^(total) _(RT-old, incoming): is the resistance of the incoming    segment to absolute destination 14 from the route table.

Therefore, the checked incoming segment is optimized, if one of the twoabove-mentioned conditions for analyzing the resistance, based onsegments R^(Seg) or total resistance R^(total), is fulfilled. The newcharacteristics of the incoming segment are then entered into the routetable, and the specific actual segment is entered as a successor.

The flowchart for segment optimization from FIGS. 6 and 7 is shown againin detail in FIG. 10. Procedure D3 and L3 for optimizing the segments iscarried out after the first initialization and the initialization ofdestination and route sections 16, 17. To this end, a final list(List 1) is initially provided, into which already optimized segmentsare entered. During the initialization of the destination, thedestination segment is entered in this final segment. A second so-calledoptimization list (List 2) is used for storing the segments to be testedin the next optimization step. It is empty at the start of theoptimization method. The segments specified in the final list areconsidered to be the imaginary, actual position of a vehicle, and all ofthe incoming segments interconnected with this actual segment aresubjected to optimization for reasons of checking. Therefore, during theoptimization of the segments, it is initially checked if the incominglist (List 1) is empty. When the final list is empty, the optimizationof the segments is ended.

Otherwise, the actual segment is determined, in that the next segmentnot yet considered is obtained from the final list (List 1). An incomingsegment is determined for this actual segment, and the segmentoptimization already described in detail with regard to FIG. 9 iscarried out. It is then checked if all of the incoming segments of theactual segments are processed. If all of the incoming segments have notyet been optimized, the next incoming segment is determined for thecurrent actual segment, and segment optimization is also carried out forthis. After all of the incoming segments have been processed, it ischecked if all of the segments from the final list (List 1) have beenprocessed. If all of the segments from the final list have not yet beenprocessed, the next actual segment is determined, and the method isiteratively continued in this manner.

Each optimized incoming segment is introduced into the optimization list(List 2).

When all of the segments from the final list (List 1) have beenprocessed, the final list (List 1) and the optimization list (List 2)are interchanged, so that the starting point for the next optimizationsare those segments which have been optimized in the last step.

Since no more incoming segments are entered into the optimization list(List 2) during a run-through, when an optimum route is found, themethod is terminated on the basis of the interchanged lists, when nomore entries are in the final list (formerly the optimization list),that is, when there were no more optimized segments in the previousrun-through.

This theoretically-described method of the present invention is nowexplained, using FIGS. 11 through 13 as an example.

FIG. 11 shows a traffic-route network having segments k1 through k10,nodes p1 through p8, and a set, fixed route section 15, which includessegments k8, k9, and k10 and is represented with hatching. A route froma starting point 13 to a destination 14 is determined, which is optimaland mainly takes the fixed route section into account.

FIG. 12 also shows a graphic representation of the traffic-route networkfrom FIG. 11, having a route from the starting point 13 to destination14 that is optimized after the execution of the method of the presentinvention. The optimized route runs through segments k1, k5, k9, k10,and k7.

This optimized route was determined as follows, where, for the trafficroute network, it is assumed that all of the segments have a resistancevalue of 10 with the exception of segments k2 and k9. Segments k2 and k9have a resistance value of 20.

A passing list (PassList) is used for describing the fixed routesection. In this list, all of the segments of the fixed route sectionare transferred to the route search unit. The passing list (PassList)contains the following entries for the example: segment +/−k8 +/−k9+/−k10

In addition, for each route segment, a route table is generated, inwhich the characteristics of all the segments of the traffic-routenetwork within considered route section 16, 17 of the route todestination 14 to be optimized are contained. For each segment, thetotal resistance and the segment resistance in both the direction of thearrow and the direction opposite the arrow are entered. In addition, thesuccessor segment corresponding to each arrow direction is registered.Furthermore, a status identifier is provided for each segment, thestatus identifier indicating whether or not the segment belongs to afixed route section.

First of all, the route table is initialized in a first step D1 fordestination route segment 17, segment resistances R^(Seg) and totalresistances R^(total) being set to “infinite”. The successor segmentsare set to “undefined”. Since segments k8, k9, and k10 belong to thefixed route section, the status identifier of these segments is set toPass. The following table is generated for destination route segment 17,which is, however, also identical in step L1 for the initialization ofthe route table for starting route segment 16: Seg- +Suc- ment Status+R^(Total) +R^(Seg) cessor −R^(Total) −R^(Seg) −Successor k1 — ∞ ∞ — ∞ ∞— k2 — ∞ ∞ — ∞ ∞ — k3 — ∞ ∞ — ∞ ∞ — k4 — ∞ ∞ — ∞ ∞ — k5 — ∞ ∞ — ∞ ∞ — k6— ∞ ∞ — ∞ ∞ — k7 — ∞ ∞ — ∞ ∞ — k8 Pass ∞ ∞ — ∞ ∞ — k9 Pass ∞ ∞ — ∞ ∞ —k10 Pass ∞ ∞ — ∞ ∞ —

In a second step D2, the optimization for destination route segment 17is initialized. In this connection, the segments from which theoptimization begins are initialized. These are all of the segments ofdestination 14. The resistances in the route table become zero forthese, and the designation, “destination”, is input as a successor, sothat the following table results: Seg- +Suc- ment Status +R^(Total)+R^(Seg) cessor −R^(Total) −R^(Seg) −Successor k1 — ∞ ∞ — ∞ ∞ — k2 — ∞ ∞— ∞ ∞ — k3 — ∞ ∞ — ∞ ∞ — k4 — ∞ ∞ — ∞ ∞ — k5 — ∞ ∞ — ∞ ∞ — k6 — ∞ ∞ — ∞∞ — k7 — 0 0 Desti- 0 0 Destination nation k8 Pass ∞ ∞ — ∞ ∞ — k9 Pass ∞∞ — ∞ ∞ — k10 Pass ∞ ∞ — ∞ ∞ —These segments are introduced into the final list (List 1) of thesegments to be optimized, which obtains, by this means, the followingappearance.

The segments of the graph are optimized in a third step D3. Theoptimization of destination segment 17 is carried out for all of theoptimization relationships, on the basis of the optimization ruledescribed above in detail with reference to, in particular, FIG. 9. Thefollowing route table is generated after the complete, iterativeoptimization of the graph. Seg- +Suc- ment Status +R^(Total) +R^(Seg)cessor −R^(Total) −R^(Seg) −Successor k1 — 40 40 +k2 50 50 +k1 k2 — 3030 +k3 50 50 +k2 k3 — 10 10 −k7 20 20 +k3 k4 — 60 60 +k1 60 60 −k1 k5 —40 40 +k2 40 40 +k9 k6 — 20 20 +k3 20 20 +k10 k7 — 0 0 Desti- 0 0Destination nation k8 Pass 40 40 +k9 50 50 +k8 k9 Pass 30 30 +k10 50 50+k9 k10 Pass 10 10 +k7 20 20 +k10

The segments of the fixed route section having status identifier “Pass”and having the lowest resistance to the destination may be ascertainedfrom this route table. For this example, these include only segment+k10, which has a resistance of 10 and represents the starting point forcalculating starting route segment 16.

The optimization of the starting route segment is carried out asfollows:

The route table is initialized in a first step L1, as is alreadydescribed with reference to step D1.

The optimization is initialized in a second step L2, whereby thesegments, from which the optimization starts, must be initialized. Forstarting route segment 16, these are the segments of the fixed routesection having status identifier “Pass” and the lowest resistance to thedestination of destination route segment 17. For these segments, theresistance previously determined during the optimization of destinationroute segment 17 is entered into the route table, and the successor isappropriately indicated. Segment resistance R^(Seg), based on thestarting route segment, for all of the segments of the fixed routesection is then set to zero, so that the route table has the followingappearance: Seg- +Suc- ment Status +R^(Total) +R^(Seg) cessor −R^(Total)−R^(Seg) −Successor k1 — ∞ ∞ — ∞ ∞ — k2 — ∞ ∞ — ∞ ∞ — k3 — ∞ ∞ — ∞ ∞ —k4 — ∞ ∞ — ∞ ∞ — k5 — ∞ ∞ — ∞ ∞ — k6 — ∞ ∞ — ∞ ∞ — k7 — ∞ ∞ — ∞ ∞ — k8Pass ∞ 0 — ∞ 0 — k9 Pass ∞ 0 — ∞ 0 — K10 Pass 10 0 — ∞ 0 —

The above-determined segments of the fixed route section having thelowest resistance to the destination of destination route segment 17 arerecorded in the final list (List 1) of the already optimized segments.The final list then has the following appearance:

The segments of the graph undergo expanded optimization in third stepL3. In this connection, the optimization of the starting route segment16 for all of the optimization relationships occurs on the basis of theoptimization rules described in detail with reference to FIG. 9. Thefollowing route table is generated after the complete optimization ofthe graph: Seg- +Suc- ment Status +R^(Total) +R^(Seg) cessor −R^(Total)−R^(Seg) −Successor k1 — 50 20 −k5 60 20 −k4 k2 — 40 30 −k6 50 20 −k5 k3— 40 20 −k7 30 20 −k6 k4 — 60 20 +k4 50 10 +k8 k5 — 50 20 −k5 40 10 +k9k6 — 30 20 −k6 20 10 +k10 k7 — 40 20 −k7 30 10 −k10 k8 Pass 40 0 +k9 500 +k8 k9 Pass 30 0 +k10 50 0 +k9 k10 Pass 10 0 — 20 0 +k10

The route list, which is generated from the two route tables forstarting route segment 16 and destination route segment 17, is compiledin the next step.

In this connection, starting out from the segment of the current vehicleposition, in this case starting position 13, the segments are writteninto the route list in accordance with the successor interlinkage ofstarting segment 16 entered in the route table, until a successor is nolonger present. The successor interlinkage of the destination routesegment is then written into the route list, until destination segmentk7 of destination 14 is reached. The optimized route is provided intabular form in the route list as a result.

The route list has the following entries for the example: +ResistanceSuccessor to No. Segment to Destination Destination 1 +k1 50 −k5 2 −k540 +k9 3 +k9 30 +k10 4 +k10 20 +k7 5 +k7 10 6 0

In the exemplary traffic-route network, this route list appears assketched in the graph of FIG. 12.

FIG. 13 shows an optimized route, after the vehicle has deviated fromthe optimized route outlined in FIG. 12. A new, optimized route is thenfound in accordance with the above-described method, the vehicle beingled over segment k6 to segment k10 of the fixed route section.

Since the method is carried out in a reverse-iterating manner from aspecific starting point, i.e., from a current vehicle position, and isnot static, an optimum route from the current, actual position to thedestination may be determined at any time, taking into consideration theusage of the fixed route section, without forcing the vehicle to turnaround and leading it back on the optimum route determined earlier.

The different effects on the course of the route from fixingintermediate destinations and route areas (ViaAreas), as well as fromfixing route sections in accordance with the present invention, aresubsequently shown.

FIG. 14 shows a normal route between a starting point 13 and adestination 14. This route runs directly from starting point 13 todestination 14 and is, therefore, optimally short but does not takefixed route section 15 into consideration.

FIG. 15 shows a route that uses an intermediate destination 18, theroute being the optimal one between starting point 13 and the edge ofintermediate destination 18, regardless of the subsequent route sectionto the separate, actual destination. An attempt is made to reach theintermediate destination as rapidly or optimally as possible.

FIG. 16 shows a route that uses a route area (ViaArea) 19, where none ofthe individual route sections is optimal by itself. Rather, the entireroute is optimized. Fixed route area (ViaArea) 19 is indicated by adotted line. While taking fixed route areas 19 into consideration in theoptimization method, where and how much route area 19 is considered inthe route is not particularly significant. However, FIG. 17 shows aroute calculated according to the method of the present invention, usinga fixed route section 15 marked by a dotted line. In this connection,two parts of the route are optimal, namely the route part betweenstarting point 13 and fixed route section 15, as well as the route partbetween the fixed route section and destination 14. Between the entrypoint and exit point, the part of the route inside fixed route section15 is also optimal again, by itself.

The entire route is optimized in this manner, it being ensured that theroute runs through fixed route section 15 as much as possible.

1-10. (canceled).
 11. A method for calculating an optimum route in a traffic-route network, taking into consideration a predefined route section, comprising: describing the traffic-route network by segments representing traffic-route sections, each segment being weighted with a respective resistance; calculating a route from a starting segment to a destination segment, taking into consideration the predefined route section, initially optimizing a part of the route extending from the predefined route section to the destination segment so that resistance to the destination is minimized; and evaluating a part of the route extending from a starting segment to the predefined route section for the least resistance to both the destination segment and the predefined route section.
 12. The method of claim 11, further comprising: dividing the route into at least two route portions including a first portion extending from the starting segment up to approximately the end of the predefined route section, and a second portion extending from approximately the end of the predefined route section up to the destination segment; separately optimizing the first portion and the second portion; and determining the optimum route from the results of the optimization for the first portion and the second portion.
 13. The method of claim 12, wherein a route is defined as optimal for an incoming segment that is interconnected with a specific segment to be tested when one of: i) the resistance of the route, defined as being currently optimal for the incoming segment, is less optimal than the resistance of a new route starting from the incoming segment, using the actual segment; and ii) the resistance of the route, defined as currently optimal for the incoming segment, corresponds to the resistance of a new route starting from the incoming segment, using the actual segment, and the resistance of the route defined as being currently optimal for the incoming segment with reference to the entire route, is less optimal than a total resistance of the entire, new route starting from the incoming segment, using the actual segment.
 14. The method of claim 13, wherein: a) the second route portion is optimized first; b) the first route portion is optimized subsequently; and c) the optimum route is determined from the results of the optimization of the first and second route portions.
 15. The method of claim 13, further comprising: initializing a route table for the first route portion and the second route portion, the route table having all possible segments of the traffic-route network for the route in the specific route segment, the initialization being such that each segment has one resistance per direction of a segment and each resistance includes a subsequent segment number; wherein, for the initialization, the resistances are set to an extreme value and subsequent segments are set to undefined.
 16. The method of claim 15, further comprising: initializing original segments, from which the optimization is started, to optimize the route in the second route portion; and setting the resistance of the original segments in the route table to zero and setting corresponding successor segments to unavailable.
 17. The method of claim 16, further comprising: initializing original segments to optimize the first route portion, wherein starting segments of the destination segment having the lowest resistance up to the second route portion are provided as the original segments; setting a total resistance of the original segments to the value determined during the optimization of the second route portion for the original segment; and setting the resistances for the segments of the predefined route section to zero, with respect to the first route portion.
 18. The method of claim 17, wherein the initialization is carried out at the start of the optimization of the first route portion and the second route portion.
 19. The method of claim 15, wherein the route table includes a status identifier for each segment of the predefined route section.
 20. The method of claim 15, further comprising: saving optimized segments in a segment list.
 21. A computer program having program codes for implementing calculation of optimum routes in a traffic-route network, taking into consideration a predefined route section, the program codes performing, when executed on a processing unit, the following: describing the traffic-route network by segments representing traffic-route sections, each segment being weighted with a respective resistance; calculating a route from a starting segment to a destination segment, taking into consideration the predefined route section, initially optimizing a part of the route extending from the predefined route section to the destination segment so that resistance to the destination is minimized; and evaluating a part of the route extending from a starting segment to the predefined route section for the least resistance to both the destination segment and the predefined route section. 